A proposal to pay women in Italy not to have abortions was rapidly gaining momentum yesterday as politicians of right and left alike gave it their endorsement.

The scheme - put forward by the left - came against a background of mounting pressure from the Roman Catholic church for a rethink of the country's 1978 abortion law. With a general election due in four months, both sides are keen to woo the decisive Catholic vote.

Under the scheme women in straitened economic circumstances would get between €250 (£170) and €350 a month for up to six months before giving birth. The plan is outlined in a proposed amendment to next year's budget sponsored by a group of MPs that includes two former women ministers - one an ex-Communist and the other from the centre-left.

Their move is the latest development in a burgeoning controversy over abortion in Italy. Last month Silvio Berlusconi's health minister, an opponent of the 1978 law, said he wanted to put pro-life volunteers into state-funded abortion advice centres to discourage women from terminating their pregnancies.

The language issuing from the Vatican has grown stronger in recent weeks with one cardinal describing abortion as "the worst kind of murder". On Wednesday a parliamentary committee gave the go-ahead for a commission of inquiry into the workings of Italy's act, passed at a time when the feminist lobby in Italy was stronger and more active than today.

One reason why the latest initiative has gathered support is that it addresses Italy's failure to produce enough children. In 2003 the fertility rate - the number of children per woman of childbearing age - was only 1.27, one of the lowest in the world. A slight increase in recent years has been due to immigrant mothers.

The low fertility rate threatens to undermine competitiveness and make Italy's welfare system unsustainable. Giuseppe Fioroni, one of three MPs sponsoring the budget amendment, said: "We want to prevent children being considered as luxury goods in the way that they are now."

The baby bonuses would be made available to two kinds of beneficiary. Single women with an income of less than €25,000 a year would be entitled to €350 a month from the start of the third month of their pregnancy. Those who were unemployed or working on temporary contracts, with a family income of less than €40,000 a year, would get €250 a month from the start of the sixth month. Italy's 2006 budget already includes other maternity incentives.

Monsignor Elio Sgreccia of the Pontifical Academy for Life welcomed the latest proposal. "It is the same method used by the pro-life movement, funded by contributions from volunteers," he said.

Rocco Buttiglione, a staunchly Roman Catholic member of Mr Berlusconi's cabinet, said research showed "a significant share of abortions - between 10% and 15% - take place for economic reasons".

But some on the left were wary of the plan. The Social Democrat leader, Enrico Boselli, said that what was needed was a comprehensive maternity policy. He accused the church of mounting "a campaign to demonise" the 1978 law and criticised fellow opposition leaders for failing to stand up to the Vatican.

Italy's legislation provides for abortion on demand in the first 12 weeks of pregnancy. However, last year a cross-party majority of MPs succeeded in bringing in a law on assisted fertilisation that gave embryos full rights from the point of conception. Since then supporters of the existing legislation have been expecting that it could be used to prise open the 1978 law. Controversy erupted again last month when the church criticised trials of the abortion pill, Mifepristone.